it's when u use a word in a position referin' to something else either than it's real meanin', it may also be a sentence.

EX #1:
A: u into video games or u'r one of'em?
B: i dont like video games
A: so u'r one of'em
B: no
A: u like video games then?
B: I DONT
A: so u'r one of'em WHO r not into video games... i got u
B: Oops! word game

Ex #2:
A: have u seen Will Smith's Movie Hancock?
B: no, but i saw Hanpussy